Film Version In the film Smooth Talk (based on "Where Are You Going, Where Have You Been?"), why do you think the director chose to change the ending?
Directors and producers almost always change something in the film versions of books and literature. Most of the time it has to do with time constraints--the book always is ten times better since there is more to it (detail, characters' thoughts and motives, dialogue, etc. which helps the reader connect with characters and understand the story). In the film which typcially aims for 2-3 hours tops, much has to be cut down, cut out or changed to fit the time most people can watch a movie without walking out, falling asleep, or losing interest in some other way.
Of course, there is always the idea that the movie has to make money. If the director or producer think that the original ending or other parts of the book/movie script aren't interesting enough or full of enough drama, they take creative license to change it. This way, they feel that there is a better chance that the movie will make lots of money, and in turn, fill their own pockets and puff up their reputations for greatness.